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1. Tetracycline targets ribosome’s bacteria. First it binds to the small subunit of the bacterial ribosome. Next it distorts the structure of the ribosomal subunit, causing incoming amino acid carrying tRNA molecules to be unable to interact correctly with the mRNA. Antibiotic resistance to Tetracycline occurs through three known mechanisms. The first mechanism is called antibiotic efflux. A protein located in the cytoplasmic membrane of the bacteria actively pumps tetracycline out of the bacterial cell through an efflux pump. The second type of resistance is called ribosome protection-type tetracycline resistance. Through this mechanism, the cytoplasmic membrane contains a protein that protects the ribosome by changing it to no longer bind to tetracycline and still be able to synthesize proteins. The third type of resistance involves an enzyme which chemically modifies tetracycline and leaves it inactive. It is not known how this enzyme is able to perform this. The described form of resistance has been found only in Bacteroides species which normally live in the human intestinal tract and can cause infections. One way that humans have contributed to Tetracycline resistance is through dermatologist prescribing the antibiotic to treat acne. Often the drug is taken for long periods of time, even years. Another way that humans have contributed to tetracycline resistance is through use in agriculture as a growth promoter. One last mode that humans contribute to resistance is through use of oxytetracycline by fruit growers to prevent disease.

3. Quorom sensing involves changes in gene expression in response to cell population densities. Autoinducer is produced and released by quorum sensing bacteria. These bacteria also have a receptor which is able to detect the autoinducer. When a high concentration of bacteria is present, more autoinducer is made. A minimal threshold of autoinducer results in an alteration of gene expression. Quorom sensing can be used to benefit bacteria in several ways. Pseudomonas aeruginosa is one type of bacterium that utilizes quorum sensing. It achieves this by producing biofilms at high population densities. This is advantageous to the bacterium because biofilms are dense layers of proteins, lipids, and sugars that form a coating around the bacteria. This protective layer keeps the bacteria safe from the immune system, antibiotics, antiseptics, etc. and increases its ability to cause disease. Yersinia pestis is another example of a bacterium that uses quorum sensing.NO, Y. pestis doesn't use q.s. to control expression of plasminogen activator or hemagglutinin!!
Its sigma factor for plasminogen expressed at 37° C. Plasminogen is advantageous to the bacteria because it prevents blood clots and allows blood to flow easier. This prevents immune cells from traveling to were the bacteria is located. This allows Yersinia pestis to inhabit blood and lymph nodes, eventually killing its host.